Essentially catheters and in particular intravenous catheters are of two overall types. The first type is a through the needle catheter in which the tubular catheter product is emplaced in a vein by being carried within a tubular needle. Once implanted the needle is withdrawn and either split to remove it from the catheter or left in a contained condition on the catheter. Through the needle catheters, however, are in limited use due to their difficulty of use and the difficulty of removing the needle. Further the needle being larger than the catheter creates a larger opening upon insertion than the outer diameter of the catheter. This permits blood leakage around the outer area of the catheter unless a swelling catheter is used.
The second and more prevalent type of catheter is the over-the-needle catheter in which a tubular catheter is placed over an inserting sharpened cannula or needle. The needle is used to pierce the skin and enter the vein of the patient and the catheter is thereafter threaded off the needle and the needle removed. This permits coupling of the catheter to medical equipment.
In an over-the-needle catheter situation, the health care worker is exposed to the sharpened tip of the cannula and to the surface of the cannula which may be contaminated with bodily fluids. Therefore, many efforts have been made to protect the health care worker from exposure to the risk of this occurrence.
U.S. Pat. No. 4,725,267 to Vaillancourt relates particularly to a post injection needle sheath and not to a catheter. The needle sheath encloses the sharpened end of a needle which is used with a syringe. The sheath is initially in a compact and secured condition on the needle hub and has a substantial portion of the needle exposed for insertion into a patient or vial. After use the sheath is extended over the needle and a cap caps the needle in order to prevent puncture of the health care worker.
U.S. Pat. No. 4,747,831 chose an automatic catheter device in which the inserting cannula is withdrawn into a housing through the operation of a spring.
U.S. Pat. No. 4,762,516 describes an assembly of a needle catheter protector. This assembly comprises an elongated housing which mounts to the needle. A needle guard is slidably mounted within the housing and is adapted to be moved forward along the needle. Following use, the needle and housing are retracted and the needle guard permanently locks with the housing while it covers the needle.
Other patents relating to stick protection devices are U.S. Pat. Nos. 4,778,453; 4,790,828; 4,804,371, which all relate to catheter type devices. U.S. Pat. No. 4,826,490 relates particularly to a syringe type product and a movable housing for enclosing the used needle of a syringe.
U.S. Pat. No. 4,832,696 relates to an assembly of a needle and a protector for the needle. The assembly comprises an elongated housing which mounts to the needle. A needle guard is slidably mounted within the housing and is adapted to be moved forward along the needle. Following use the needle and housing are retracted and the needle guard becomes permanently locked with the housing as it covers the needle. This patent is of the same family of the '516 patent described above.
Further patents directed to needle stick protection include U.S. Pat. No. 4,834,718 entitled Safety Needle Apparatus. This patent describes an intravenous catheter apparatus which protects a clinician from accidental puncture which may result in the transfer of dangerous infections. The catheter is introduced with the aid of a needle which is thereafter withdrawn from the patient's body into a protective housing without exposing the needle during intermediate stages of the process. In particular, means are provided for latching the housing in place after the needle is withdrawn and for locking a catheter hub in place until the needle is withdrawn. Withdrawal and locking are affected in one continuous motion.
U.S. Pat. No. 5,215,528 is entitled Catheter Introducer Assembly Including Needle Tip Shield. This patent describes an assembly where a needle is modified to have an enlarged diameter near the tip. A needle tip cover is slidably mounted on the needle such that it is slid to a point wherein it engages the enlarged portion of the shaft to prevent removal of the tip therefrom. The catheter is releasably mounted over the tip cover. It is stated in this patent that the enlarged portion also serves to provide a leak proof seal between the catheter and the needle. However, it has been found in practice that a device substantially conforming to the '528 patent has significant problems. Initially if the widened portion of the needle is large enough to create the "leak proof seal" the friction on removal of the catheter may be so great as to create a commercially unacceptable apparatus. The friction upon removal of the catheter from the needle must be low enough to permit ease of removal of the needle. In order to provide this low friction the expansion of the needle cannot engage the inner portion of the tubular catheter tightly enough to provide the "leak proof seal". Therefore, catheters of this design leak a significant amount around the needle and in the space between the needle and catheter. Such a structure and device are self defeating in that the exposure to the blood is increased through the leakage rather than decreased through the use of a cover and tip protection device.